St. Juliana of Liège
The institution of Corpus Christi as a feast in the Christian calendar resulted from approximately forty years of work on the part of Juliana of Liège, a 13th-century Norbertine canoness, also known as Juliana de Cornillon, born in 1191 or 1192 in Liège, Belgium, a city where there were groups of women dedicated to Eucharistic worship. Guided by exemplary priests, they lived together, devoted to prayer and to charitable works. Orphaned at the age of five, she and her sister Agnes were entrusted to the care of the Augustinian nuns at the convent and leprosarium of Mont-Cornillon, where Juliana developed a special veneration for the Blessed Sacrament.
She always longed for a feast day outside of Lent in its honour. Her vita reports that this desire was enhanced by a vision of the Church under the appearance of the full moon having one dark spot, which signified the absence of such a solemnity. In 1208, she reported her first vision of Christ in which she was instructed to plead for the institution of the feast of Corpus Christi. The vision was repeated for the next 20 years but she kept it a secret. When she eventually relayed it to her confessor, he relayed it to the bishop.
Juliana also petitioned the learned Dominican Hugh of St-Cher, and Robert de Thorete, Bishop of Liège. At that time bishops could order feasts in their dioceses, so Bishop Robert ordered in 1246 a celebration of Corpus Christi to be held in the diocese each year thereafter on the Thursday after Trinity Sunday.
Hugh of St-Cher travelled to Liège as Cardinal-Legate in 1251 and, finding that the feast was not being observed, reinstated it. In the following year, he established the feast for his whole jurisdiction (Germany, Dacia, Bohemia, and Moravia), to be celebrated on the Thursday after the Octave of Trinity (one week later than had been indicated for Liège), but with a certain elasticity, for he granted an indulgence for all who confessed their sins and attended church "on a date and in a place where [the feast] was celebrated".
Jacques Pantaléon of Troyes was also won over to the cause of the Feast of Corpus Christi during his ministry as Archdeacon in Liège. It was he who, having become Pope as Urban IV in 1264, instituted the Solemnity of Corpus Christi on the Thursday after Pentecost as a feast for the entire Latin Church, by the papal bull Transiturus de hoc mundo. The legend that this act was inspired by a procession to Orvieto in 1263, after a village priest in Bolsena and his congregation witnessed a Eucharistic miracle of a bleeding consecrated host at Bolsena, has been called into question by scholars who note problems in the dating of the alleged miracle, whose tradition begins in the 14th century, and the interests of Urban IV, a former Archdeacon in Liège. Though this was the first papally imposed universal feast for the Latin Church, it was not in fact widely celebrated for half a century, although it was adopted by a number of dioceses in Germany and by the Cistercians, and in 1295 was celebrated in Venice. It became a truly universal feast only after the bull of Urban IV was included in the collection of laws known as the Clementines, compiled under Pope Clement V, but promulgated only by his successor Pope John XXII in 1317.
While the institution of the Eucharist is celebrated on Holy (Maundy) Thursday, the liturgy on that day also commemorates Christ's , the institution of the priesthood and the agony in the Garden of Gethsemane. So many other functions took place on this day that the principal event was almost lost sight of. This is mentioned in the Bull Transiturus as the chief reason for the introduction of the new feast. Hence, the feast of Corpus Christi was established to create a feast focused solely on the Holy Eucharist.
Three versions of the office for the feast of Corpus Christi in extant manuscripts provide evidence for the Liège origins and voice of Juliana in an original office, which was followed by two later versions of the office. A highly sophisticated and polished version can be found in BNF 1143, a musical manuscript devoted entirely to the feast, upon which there is wide scholarly agreement: the version in BNF 1143 is a revision of an earlier version found in Prague, Abbey of Strahov MS D.E.I. 7, and represents the work of St. Thomas Aquinas following or during his residency at Orvieto from 1259 to 1265. The office can also be found in the 1343 codex Regimen Animarum.:13 This liturgy may be used as a votive Mass of the Blessed Sacrament on weekdays in ordinary time. The hymn Aquinas composed for Vespers of Corpus Christi, Pange Lingua or another eucharistic hymn, is also used on Maundy Thursday during the procession of the Blessed Sacrament to the altar of repose. The last two verses of Pange Lingua are also used as a separate hymn, Tantum Ergo, which is sung at Benediction of the Blessed Sacrament. O Salutaris Hostia, another hymn sung at Benediction of the Blessed Sacrament, comprises the last two verses of Verbum Supernum Prodiens, Aquinas' hymn for Lauds of Corpus Christi. Aquinas also composed the propers for the Mass of Corpus Christi, including the sequence Lauda Sion Salvatorem. The epistle reading for the Mass was taken from Paul's First Epistle to the Corinthians (1 Corinthians 11:23-29), and the Gospel reading was taken from the Gospel of John (John 6:56-59).
When Pope Pius V revised the General Roman Calendar (see Tridentine Calendar), Corpus Christi was one of only two "feasts of devotion" that he kept, the other being Trinity Sunday. In that calendar, Corpus Christi was celebrated on the Thursday after Trinity Sunday. The feast had an octave until 1955, when Pope Pius XII suppressed all octaves, even in local calendars, except those of Christmas, Easter and Pentecost (see General Roman Calendar of Pope Pius XII).
From 1849 until 1969, a separate Feast of the Most Precious Blood of Our Lord Jesus Christ was assigned originally to the first Sunday in July, later to the first day of the month. This feast was removed from the General Roman Calendar in 1969, "because the Most Precious Blood of Christ the Redeemer is already venerated in the solemnities of the Passion, of Corpus Christi and of the Sacred Heart of Jesus and in the feast of the Exaltation of the Holy Cross. But the Mass of the Most Precious Blood of Our Lord Jesus Christ is placed among the votive Masses".